A weather event can have a myriad of associated attributes. For example, attributes associated with rainfall include character, amount, duration, and infiltration. The character of rainfall can be, e.g., light, medium, or heavy. The amount of rainfall can be measured by the depth of the rain accumulating in, e.g., an open square container that is 1 meter wide, 1 meter long, and 0.5 meters high. If rain accumulates in the box to a depth of 35 millimeters, then the amount of rainfall is 35 millimeters per square meter. The duration of the rainfall is the time of the rainfall from start to finish, e.g., 3.5 hours.
Infiltration refers to the physical process involving movement of rain water through the boundary area where the atmosphere interfaces with the soil. This movement is governed by surface soil conditions, such as porosity and permeability. Typically, the rate at which rain water infiltrates the soil depends on the puddling of the water at the soil surface by the impact of raindrops, the texture and structure of the soil, the initial soil moisture content, the decreasing water concentration as the rain water moves deeper into the soil, filling of the pores in the soil matrices, changes in the soil composition, and the swelling of the wetted soils that in turn close cracks in the soil. As rain falls, rain water reaching the ground surface infiltrates into the soil until the infiltration capacity of the soil is exceeded. Thereafter, surface puddles, ditches, and other depressions are filled, and then surface runoff is generated. Surface runoff is the water flow that occurs when soil is infiltrated to full capacity, and excess water flows over the land.